linux-kernel - Re: Linux 4.19 and GCC 9

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Date:   Fri, 17 May 2019 10:23:10 -0700
From:   Ivan Babrou <ivan@...udflare.com>
To:     Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc:     Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        kernel-team <kernel-team@...udflare.com>
Subject: Re: Linux 4.19 and GCC 9

On Fri, May 17, 2019 at 8:22 AM Arnaldo Carvalho de Melo
<arnaldo.melo@...il.com> wrote:
>
> Em Fri, May 17, 2019 at 11:01:45AM +0200, Miguel Ojeda escreveu:
> > On Fri, May 17, 2019 at 10:51 AM Greg KH <gregkh@...uxfoundation.org> wrote:
> > >
> > > On Fri, May 17, 2019 at 10:35:29AM +0200, Miguel Ojeda wrote:
> > > > On Fri, May 17, 2019 at 9:38 AM Peter Zijlstra <peterz@...radead.org> wrote:
> > > > >
> > > > > Right; if there is anything you can reproduce on linus.git I'll happily
> > > > > have a look. If it doesn't reproduce all you have to do is find the
> > > > > patches that make it work and ask Greg.
> > > >
> > > > Just to clarify: Linus' master is clean of these issues with GCC 9.1.1.
> > >
> > > Great!  Care to find the patches that did that work and send me the git
> > > commit ids so that I can queue them up?  I don't have gcc9 here yet on
> > > my systems, so I can not test for this.
> >
> > I am unsure about the perf and the objtools parts (Peter/Josh?), but
>
> I'm not noticing these while building upstream perf with gcc 9.1.1 on at
> least fedora:30.
>
>     33  fedora:30                     : Ok   gcc (GCC) 9.1.1 20190503 (Red Hat 9.1.1-1)

I've tried to replicate this in fedora:30 docker container and it's there:

[root@...uxkit-025000000001 perf]# gcc --version
gcc (GCC) 9.1.1 20190503 (Red Hat 9.1.1-1)

[root@...uxkit-025000000001 perf]# pwd
/tmp/linux-4.19.44/tools/perf

[root@...uxkit-025000000001 perf]# make -j1
...
trace/beauty/ioctl.c: In function ‘ioctl__scnprintf_kvm_cmd’:
trace/beauty/ioctl.c:85:82: error: array subscript [-2147483648, -1]
is outside array bounds of ‘const char *[0]’ [-Werror=array-bounds]
   85 |  if (nr < strarray__kvm_ioctl_cmds.nr_entries &&
strarray__kvm_ioctl_cmds.entries[nr] != NULL)
      |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
In file included from trace/beauty/ioctl.c:82:
/tmp/linux-4.19.44/tools/perf/trace/beauty/generated/ioctl/kvm_ioctl_array.c:1:20:
note: while referencing ‘kvm_ioctl_cmds’
    1 | static const char *kvm_ioctl_cmds[] = {
      |                    ^~~~~~~~~~~~~~
In file included from /usr/include/string.h:494,
                 from util/debug.h:7,
                 from builtin-help.c:15:
In function ‘strncpy’,
    inlined from ‘add_man_viewer’ at builtin-help.c:192:2,
    inlined from ‘perf_help_config’ at builtin-help.c:284:3:
/usr/include/bits/string_fortified.h:106:10: error:
‘__builtin_strncpy’ output truncated before terminating nul copying as
many bytes from a string as its length [-Werror=stringop-truncation]
  106 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest));
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
builtin-help.c: In function ‘perf_help_config’:
builtin-help.c:187:15: note: length computed here
  187 |  size_t len = strlen(name);
      |               ^~~~~~~~~~~~
trace/beauty/ioctl.c: In function ‘ioctl__scnprintf_perf_cmd’:
trace/beauty/ioctl.c:109:84: error: array subscript [-2147483648, -1]
is outside array bounds of ‘const char *[0]’ [-Werror=array-bounds]
  109 |  if (nr < strarray__perf_ioctl_cmds.nr_entries &&
strarray__perf_ioctl_cmds.entries[nr] != NULL)
      |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
In file included from trace/beauty/ioctl.c:106:
/tmp/linux-4.19.44/tools/perf/trace/beauty/generated/ioctl/perf_ioctl_array.c:1:20:
note: while referencing ‘perf_ioctl_cmds’
    1 | static const char *perf_ioctl_cmds[] = {
      |                    ^~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

> > about the -Wmissing-attributes I cleaned, they were these:
>
> > a6e60d84989f ("include/linux/module.h: copy __init/__exit attrs to
> > init/cleanup_module")
> > c0d9782f5b6d ("Compiler Attributes: add support for __copy (gcc >= 9)")
> > ff98e20ef208 ("lib/crc32.c: mark crc32_le_base/__crc32c_le_base
> > aliases as __pure")
> >
> > Cheers,
> > Miguel
>
> --
>
> - Arnaldo